GEOMORPHOLOGY in STRABO's GEOGRAPHY Norman J. W. THROWER 11
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GEOMORPHOLOGY IN STRABO'S GEOGRAPHY I NoRMAN J. W. THROWER University of California, Los Angeles Modern advances ·in geomorphology command so much attention that ancient writings on this subject are often overlooked. Excellent works in the history of science, such as the geological source book of Mather and Mason,l freguently include only contributions of the ast three or four centuries. Although, apparently, little heed is now paiJ to. early consider ations of landforms and their development, this was not always the case. Some of the greatest contributors to earth science in the nineteenth century were well aware of the considerable understanding among the ancients regarding geomorphological processes. Thus, Sir Charles LyelP commends Strabo of Amasia for anticipating some of the conclusions of modern earth science. Strabo is praised by Alexander von Humboldt3 and Sir Archibald Geikie'1 also calls attention to the sagacious observations of Strabo upon the physical earth. Among ancient writings on geomorphology Strabo's Geography is of special value because, in addition to stating his own views, the author comments upon or summarizes earlier work in earth science, much of which is lost to us in the original. An examination of Strabo's writings, therefore, provides a good basis for understanding early concepts of land form genesis, process arid change. Our knowledge of Strabo's life is based on scattered references in his Geography. He was born at Amasia in Pontus (northeast Turkey) about 63 B.C. Strabo was partly Greek by ancestry and received a good Greek education; at different periods of his life he was a student of Aristodemus (tutor of Pompey's sons), of Tyrannion (tutor of Cicero's sons) and of Xenarchus. Probably under these teachers Strabo developed an interest in the physical earth, but this was undoubtedly stimulated by his extensive travels. According to his own testimony, Strabo journeyed from Armenia to Tuscany and from Pontus to Ethiopia (2:5:11V He was familiar with a number of the important cities of the Mediterranean and resided for considerable periods in Rome and Alexandria. While in Egypt he traveled up the Nile as far as the First Cataract. It was probably after his return to Pontus that Strabo devoted himself to the writing of his encyclopedic Historical Memoirs. This great compila tion, which consisted of forty-three volumes on ancient history, is lost to us except for fragments included in the work of other authors or in Strabo's 1 Kirtley F. Mather and Shirley L. Mason, A Source Book in Geology (New York, McGraw-Hill, 1939), p. vii. 2 Charles Lyell, Principles of Geology (London, J. Murray, 1830), Vol I, p. 18. 3 Kosmos Alexander von Humboldt, (Stuttgart· a!ld Tubingen, J G. Cotta, 1845), Vol. 1, p. 223. 4 Archibald Geikie, The Fotmclers of Geology (London, Macmillan, 1905), p. 18. 5 Numbers in parentheses within the text refer respectively to book, chapter, and paragraph in The Geography of Strabo (Loeb Classical Library) with an Eng- lish translation by H. L. Jones (London, William Heinemann). - 11 own surviving writings. After finishing the history Strabo commenced his Geograz;hy, which may have been completed only a short time before his death in 20 A.D. · Except for minor omissions, Strabo's Geography has come down to us complete. The whole work consists of seventeen books in which the author attempts to bring togeth,er all geographical knowledge of his day. The fin;t two books, which are topical and systematic in character, form a general introduction to the subject. In the remaining fifteen books Strabo is con· cemed mainly with regional description, treating first Europe, then Asia and finally Africa. It is difficult to form any reliable estimate of Strabo's own contribution to earth science. Mathematical geography he neglects entirely except where he disputes the opinions of others or reports their findings, but as the result of this we are indebted to Strabo for part of our knowledge of the work of Eratosthenes, Hipparchus and Poseidonius. In addition to these authorities, Strabo cites the work of a score of other Greek natural philosophers. Strabo's Geography wJs a popular work among European scholars in the later Middle Ages. Among more recent admirers of Strabo's writings was Napoleon Bonaparte, who authorized an important French translation of the Geography. Accepting cosmological ideas prevailing among Greek philosophers who preceded him, Strabo believed in the geocentric theory of the universe (2:5:2). Although according to this view the earth is regarded as a motion less planet, Strabo understood that the surface of the earth is constantly undergoing change. He reports the opinion of Eratosthenes that successive changes in the form of the earth have been occasioned by water, fire, earthquakes and eruptions, but criticizes the earlier author for over-empha sizing the magnitude of the resulting surface irregularities (I :3:3 ). Echoing the ideas of other writers, Strabo asserts that land and water do not remain in fixed places. As evidence of that he notes the occurrence of marine fossils and salt beds at considerable distances from the sea, and quotes the opinions of several earlier authorities on the matter. In parti cular, Strata the Philosopher is cited by Strabo as believing that the water !evels of different seas vary and that there had been changes of water level · in the past (I: 3:4 ). The Black Sea, Strabo suggested, was formerly without an outlet and had received so much water from rivers emptying into it that the surrounding land had beeri flooded.6 Eventually a natural passage was forced through the Dardanelles, the water level lowered, and fossils which had been deposited along the old shore zone were revealed to view. Strata applied a similar explanation to the Mediterranean Sea which, he thought, had broken its banks at Gibralt1r and left large areas, especially in the Levant, dry, fossiliferous and saline. Strabo rejects Strata's thesis, and proposes instead that it is the level of the strata on which the waters rest, rather than the water level itself, which changes (I: 3: 5). Of this idea of Strabo's, LyeW writes enthusiastically. 6 The hydrological cycle was not understood until the late seventeenth century, notably under Edmund Halley. r Lyell, lac. cit. 12 Strabo had unusually good opportunities for observing the effects of vulcanism in Italy, and gives accounts of the phenomena in that country, in Sicily and in Greece. He was aware of the volcanic nature of the Naples area and in his description of Vesusvius informs us that the character of the rocks suggests that in the past it had been in an active state (5:4:8).8 However, like his predecessors he believed that volcanoes became extinct because of lack of fuel. Strabo noted the similarity between the Naples region, the Lipari Islands and the region around Etna in Sicily. In one place he expresses the opinion that certain of the offshore islands were built up from the sea by volcanoes rather than broken off from the main land as suggested by other authorities (l: 3: 10). Before the formation of Etna, Strabo reports, the Strait of Sicily suffered greatly from earthquakes, but, because the large crater and its subsidiary cones act as safety valves, shocks had become less frequent and less severe (6: I :6). Commenting upon this, Geikie0 observes, "The doctrine that volcanoes are safety valves, which was once thought to be a modern idea, is thus at least as old as the beginning of the Christian era." Strabo relates Poseidonius' eye-witness account of the formation of a small volcano in the Lipari archipelago. In this connection Strabo comments on the relationship between winds �mel vulcanism, a belief widely held by the ancients. Volcanoes were thought to be caused by winds trapped below the earth which were fanned into act ivity by surface winds (6:2:8). Most of the allusions to vulcanism in the Geography refer to the Tyrrhenian region, while his examples of seismic activity are taken largely from the eastern Mediterranean. Strabo calls attention to a number of cases of the destruction of cities by earthquakes (l :3: 19,20). There are some references to the opening up of fissures, to the effects of seismic sea waves and to temporary or permanent disturbance of drainage patterns. Examples are noted of earthquakes associated with and of those independent of vulcanism. He reports that certain peaks in Laconia were said to be broken off during an earthquake shock. The same agency is reported to have been responsible for the destruction of Helice and of an extensive coastal plain seaward of the city (8:7:2). A specific example of the alteration of drainage resulting from dias trophic activity is cited as occurring in Arcadia, where the Ladon River apparently had its sources stopped for a short period (8:8:4). More dra matic was the case of the Peneius River of Tempe in Thessaly which, after a chasm had been formed following an earthquake, changed its course to drain an area that had formerly been the bed of a lake (9: 5:2). Strabo reports several cases of rivers going underground after earthquakes had taken place, but makes no clear distinction between that type of occurrence and underground drainage resulting from solution in limestone country. Hot springs are described in several localities, and examples are noted of the formation of minor features attributed to the deposition of materials carried in solution (I 3:4: 14). It is not surprising that there are many myths concerning the origin and development of rivers since they are so important to human life.